1. Field of the Invention
The present invention relates to mechanical heat transfer systems, such as air conditioning systems, and more particularly to a apparatus and method for converting an otherwise conventional residential or commercial air conditioning system into a heat transfer system capable of cooling an interior space while simultaneously heating a body of water, such as water from a swimming pool.
2. Description of the Background Art
Mechanical air conditioning and refrigeration systems, for absorbing heat from one source and rejecting heat to another source, are well known in the art. In a conventional mechanical air conditioning system, a pair of heat exchangers are fluidly connected in a refrigeration circuit through which a heat transfer medium (hereinafter "refrigerant") flows. In a typical system an evaporator coil is in heat transfer communication with interior space, and a condenser coil is in heat transfer communication with a suitable heat sink, such as ambient air from the atmosphere. Mechanical air conditioning systems are well known in the art. Such systems may be either "packaged," wherein all of the necessary components are packaged in a single unit, or "split systems," wherein typically the evaporator is remotely located with respect to the compressor and condenser.
Furthermore, the background art reveals heat transfer systems directed to rejecting heat into a water source, such as a swimming pool, to raise and maintain the temperature of the pool water at a comfortable level. The heat transfer systems of the background art recognize the efficiency of utilzing the waste heat of condensation, which would otherwise be rejected to the atmosphere without being put to any beneficial use, to heat water from a pool or spa for recreational purposes. In warm climates, the use of the swimming pool may be limited to those months where the ambient temperature is sufficient to warm the swimming pool water to a comfortable level, especially pools that are not exposed to direct sunlight. In colder climates, swimming pool water must be continually heated in order to provide comfortable aquatic recreation. In addition, there exists a number of other needs and uses for warmed water, including domestic hot water and water used for irrigation or other commercial purposes.
A number of references are directed to providing a mechanical system for rejecting heat to a water source. For example, U.S. Pat. No. 5,560,216, issued to Holmes, discloses a combination air conditioner and pool heater. U.S. Pat. No. 5,184,472, issued to Guilbault et al., discloses an add-on heat pump swimming pool control. U.S. Pat. No. 4,232,529, issued to Babbitt et al., discloses a mechanical refrigeration system for selectively heating swimming pool water. Babbitt et al. discloses three operating modes for selectively transferring heat. In the first mode, heat is transferred from the atmosphere to pool water. In a second mode, heat is transferred from a conditioned space to the atmosphere. In a third mode, heat is transferred from the conditioned space to pool water.
There are, however, a number of inherent disadvantages present in the prior art systems. Specifically, the prior art systems fail to disclose a system or method for routine modification of installed air conditioning systems for converting a straight cool system into a system capable of selectively heating pool water. Accordingly, there exists a need for a retrofit kit for mechanical air conditioning systems, for universal use with existing or new equipment, for converting the system to enable rejected heat to be used to warm pool water. Furthermore, additional energy savings would be realized if such a modification were capable of converting a straight cool air conditioning system into a heat pump such that the interior space served by the system could be efficiently heated, such that the energy savings of a heat pump were realized.
In addition, most mechanical air conditioning systems suffer from limitations in connection with the need to maintain an adequate supply of lubricating oil in the compressor. Specifically, oil used to lubricate the compressor is routinely carried by the refrigerant through the refrigerant lines. Furthermore, systems having hermetic compressors do not have a crankcase oil return connection and must rely on the refrigerant to return sufficient oil to the compressor. When the distance between certain components (e.g. evaporator and compressor) is substantial, care must be taken to insure the compressor is not starved for oil and that sufficient oil is returned to the compressor through the refrigerant lines. Accordingly, systems with heremetic compressors have historically been limited to applications having relatively short refrigerant line length requirements. As a result, it is recognized in the background art that hermetic compressors are prone to premature compressor failure in applications wherein the heat transfer coils are substantially spaced and connected by long refrigerant line runs. The oil return problem is most pronounced in complex heat transfer systems, such as those capable of rejecting heat to multiple sources, due to the spacing of components and existence of extended refrigerant line lengths. Accordingly, there exists a need for insuring that an adequate supply of lubricating oil is returned to a hermetic compresser in complex heat transfer systems.
A further disadvantage realized by most heat transfer systems results when oil, carried by refrigerant through the system, accumulates on the interior tube walls of the heat transfer coils and acts as a heat transfer insulator thereby degrading heat transfer efficiency. Accordingly, there exists a need for a mechanical air conditioning system capable of rejecting heat to a water source wherein heat transfer efficiency is maximized, and long runs of refrigerant tubing may be accommodated, by substantially eliminating the accumulation of lubricating oil from the heat transfer surfaces by separating entrained oil from compressed gas and returning the separated oil back to the compressor.